I understand that centerfire pistol cartridges will last a very long time if kept in a cool dry environment. I've recently shot .357 Mag & .45 ACP from the late 80's and they were fine, albeit a little smokey.

So, given that the 22LR cartridge uses a heel bullet; how many years would a 22LR cartridge hold up in a similar cool/dry environment? The first part that would probably go bad would be the bullet if it was uncoated lead. But how about copper coated 22LR's?